What was found
AIRCRAFT WAS GROUNDED: FUMES ONLY ON FLIGHT DECK DURING DESCENT AND INITIAL POWER REDUCTION AT EACH STEP DOWN. FLIGHT CREW TURNED OFF ENGINE #2 BLEED. FUMES DID NOT RE-OCCUR. ODOR SMELLED LIKE A HEATER USED FOR A 1ST TIME. MAINTENANCE FOUND THE #2 ENGINE FAN AIR VALVE THERMOSTAT SENSE LINE CHAFFED AND HAD A HOLE IN IT. MAINTENANCE REPLACED THE SENSE LINE PER AMM 36-11-13. (AALA202309083815) MAINTENANCE ALSO REPLACED #2 ENGINE FAN AIR VALVE THERMOSTAT 7170HM2 PER AMM 36-11-43. (AALA202309080319) A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED.